JPH11157814A - Recovering method of rare gas and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the recovering method and device of the rare gas capable of efficiently recovering the rare gas discharged from the device using the rare gas, moreover, capable of stably supplying the rare gas having a prescribed purity to the device using the rare gas, and also capable of reducing consumption of the rare gas. SOLUTION: In the case of recovering the rare gas in a waste gas discharged from the device using the rare gas operated under the reduced pressure, an introduction of the waste gas to a recovery system and discharging to a discharge system are switched in a reduced state, and also the switching operation is executed in accordance with a concn. of an impurity component incorporated in the waste gas and the operating state of the device using the rare gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for recovering a rare gas, and more particularly, to a method for using a rare gas operated under reduced pressure, such as a plasma sputtering apparatus, a plasma CVD apparatus, and a reactive ion etching apparatus. The present invention relates to a method and an apparatus for recovering a rare gas in exhaust gas discharged.

[0002]

2. Description of the Related Art In a process of manufacturing a semiconductor device such as a semiconductor integrated circuit, an active matrix type liquid crystal panel, a solar cell panel, and a magnetic disk, a plasma is generated in a rare gas atmosphere under reduced pressure, and the plasma is generated by the plasma. Devices for performing various processes, for example, a sputtering device, a plasma CVD device, a reactive ion etching device, and the like are used.

For example, in a sputtering apparatus, the inside of a chamber is evacuated by a vacuum pump while introducing a rare gas into the process chamber at a flow rate of about 500 cc / min. A high frequency is applied to the electrode to generate plasma, and the plasma is used to sputter a solid film-forming material placed in a chamber and deposit the material on a wafer surface to form a thin film.

[0004] In a plasma CVD apparatus, a film forming gas and a rare gas are mixed and introduced into a process chamber at a flow rate of about 1000 cc / min. 1
Plasma is generated while maintaining the pressure at about 00 Pa, and a film forming gas is decomposed by using the plasma and deposited on the wafer surface heated to about 300 ° C. to form a thin film.

Further, in a reactive ion etching apparatus, while mixing an etching gas and a rare gas and introducing them into a process chamber, the pressure in the chamber is increased by several Ps.
A plasma is generated in the state of being held at a, and an etching gas is excited using the plasma, and etching is performed using the excited ions.

[0006] In such various apparatuses, since processing is performed using plasma having high energy, if a gas species other than those contributing to film formation, for example, nitrogen, oxygen, moisture, etc., is present in the processing atmosphere. Then, a predetermined thin film cannot be formed or etching cannot be performed. For example, in the case where a metal wiring for a semiconductor integrated circuit is formed using a sputtering apparatus, if moisture, oxygen, or the like is present in the atmosphere, the metal thin film is oxidized, and the resistance of the wiring increases. Further, like tantalum (Ta), the crystal structure may change. Further, in an atmosphere for forming a polycrystalline silicon thin film by plasma CVD,
The presence of oxygen, moisture, organic impurities, and the like causes various problems such as non-uniform crystal grain size and extremely reduced electron mobility. Further, if impurities are present during etching by reactive ion etching, the selection ratio of the material cannot be obtained, resulting in defective etching or damage to the wafer. Therefore, it is necessary to reduce impurities in the rare gas introduced into the apparatus utilizing plasma to several ppb or less.

FIG. 4 is a system diagram showing a sputtering apparatus as an example of a plasma processing apparatus. Usually, in such a sputtering apparatus, the process chamber 1
A loading chamber 3 for transporting the wafers 2 is installed at the preceding stage, and the wafers 2 are processed one by one. The loading chamber 3 is kept in a purge gas atmosphere such as dry air or nitrogen gas supplied from a purge gas supply unit 4 and is kept in a reduced pressure state by vacuum exhaust pumps 6 a and 6 b connected to the loading chamber 3 via a gate valve 5. ing. The unprocessed wafer 2 held in the loading chamber 3 is evacuated from the loading chamber 3 and the process chamber 1, and then passes through a gate valve 7 separating the chambers 1 and 3 from the wafer susceptor 8 in the process chamber. Installed on top.

After closing the gate valve 7 separating the chambers 1 and 3, the rare gas from which impurities have been removed through the purifier 9 is
The gas is introduced into the process chamber 1 through the gas supply device 10. Usually, in order to make the inside of the process chamber 1 a rare gas atmosphere, a cycle consisting of evacuation of the process chamber by the vacuum pumps 11 a and 11 b and introduction of the rare gas from the gas supply device 9 is performed by the control device 12. This is repeated one or more times by opening and closing each valve in a predetermined order according to a command. After the inside of the process chamber is set to a rare gas atmosphere, plasma is generated in the process chamber by applying a high frequency from a high frequency power supply 14 through a matching circuit 13, and the generated plasma sputters a solid film-forming material. A thin film is deposited on the surface. The wafer 2 on which a predetermined thin film is formed is transferred from the process chamber 1 to the next process via the loading chamber 3 for the next processing. In such a process, loading and unloading of wafers are performed about 30 times per hour.

[0009]

The exhaust gas evacuated from the sputtering apparatus via the vacuum pumps 11a and 11b is used for forming a film even if it is used for purging in a process chamber. However, it was directly discharged from the exhaust path 15 to the outside of the system. On the other hand, the rare gas supplied from the rare gas container 16 is only slightly present in the atmosphere. For example, the concentration of xenon is 0.086 ppm in the atmosphere. These rare gases are produced by further rectifying those concentrated in oxygen gas by cryogenic separation of air, and it is difficult to obtain them in large quantities.

Therefore, exhaust gas discharged from the exhaust path 15 to the outside of the system (exhaust gas when most of the exhaust gas becomes rare gas)
Is collected in a separately provided container or balloon, the collected gas is concentrated and rectified to separate a rare gas, and this is reused. According to this recovery method, since the exhausted rare gas is collected in a container or a balloon, there is an advantage that the rare gas after concentrated rectification can be used in various industrial fields. There has been a problem that the cost of transporting balloons is increased. In addition, there is a problem that a rare gas cannot be obtained with a stable purity at the time of concentration and rectification because atmospheric components are easily mixed when the container is attached or detached.

Further, as shown in FIG. 5, there has been proposed a method of recovering a rare gas in exhaust gas exhausted from a process chamber (exhaust gas when most of the exhaust gas becomes a rare gas) by a closed loop. In this method, a recovery path 23 connected to a rare gas recovery apparatus 22 is provided in an exhaust path 15 of a sputtering apparatus 21 formed in the same manner as described above, and an outlet path 24 of the rare gas recovery apparatus 22 is connected to the purifier 9. The exhaust gas (rare gas) discharged from the process chamber 1 is introduced into the rare gas recovery device 22 by switching a pair of switching valves 25a and 25b provided in the recovery path 23 and the exhaust path 15, respectively. Like that. The rare gas introduced into the rare gas recovery device 22 is pressurized to a predetermined pressure by a compressor 27 having a bypass path 26, and then merges with a rare gas that is appropriately replenished from the rare gas container 16 to the purifier 9. Where it is purified and recycled for recycling.

However, in this method, when the wafer 2 is carried in and out, impurities are mixed into the process chamber 1 due to diffusion from the loading chamber 3 and the like, and the impurity concentration in the process chamber 1 is increased as the wafer 2 is carried in and out. Because of the fluctuation, the purity immediately after the introduction of the rare gas fluctuates, and it is difficult to optimize the timing of the recovery performed by opening and closing the switching valves 25a and 25b by the controller 12. Further, the exhaust gas is recovered from the secondary exhaust path 15 of the downstream vacuum pump (back pump) 11b, and this part, that is, the secondary pressure of the downstream back pump 11b is atmospheric pressure. As a result, the gas flow rate is rapidly reduced, and not only the rare gas but also the impurity components are likely to stay inside the back pump and on the secondary side of the back pump. In this case, it is necessary to purge the outside of the system with a large amount of rare gas, and it is impossible to recover the rare gas with high efficiency by the recovery device 22 as shown in FIG. The back pump 11
When b and the impurity component and the purged rare gas retained on the secondary side thereof are recovered as they are, the absolute amount of the impurity component increases, so that the life of the purifier 9 becomes extremely short, and
There is a disadvantage that the purity of the rare gas is reduced.

Accordingly, the present invention is capable of efficiently recovering a rare gas discharged from a rare gas-using facility such as a plasma processing apparatus using a rare gas under reduced pressure, and has a predetermined purity for the rare gas-using facility. It is an object of the present invention to provide a rare gas recovery method and apparatus capable of stably supplying the rare gas and reducing the consumption of the rare gas.

[0014]

In order to achieve the above object, a method for recovering a rare gas according to the present invention is a method for recovering a rare gas from exhaust gas discharged from a rare gas-using facility operated under reduced pressure. A switching operation between the introduction of the exhaust gas into the recovery system and the discharge into the exhaust system is performed according to the concentration of the impurity component contained in the exhaust gas.

Further, in the rare gas recovery method of the present invention, when recovering the rare gas in the exhaust gas discharged from the rare gas using equipment operated under reduced pressure, the exhaust gas is introduced into the recovery system and the exhaust gas is introduced into the exhaust system. And the discharge operation of the exhaust gas to the recovery system and the discharge operation to the exhaust system are performed by changing the concentration of the impurity component contained in the exhaust gas or the rare gas. It is characterized in that it is performed according to the operating state of the equipment used.

Further, the rare gas recovery device of the present invention includes a rare gas using facility operated under reduced pressure, a first vacuum pump for sucking exhaust gas discharged from the rare gas using facility, and a first vacuum pump. A second evacuation pump provided in series on the secondary side of the evacuation pump via a decompression line, a recovery line branched from the decompression line via line switching means, and a recovery vacuum provided on the recovery line A pump, a compressor for increasing the pressure of the recovered gas derived from the recovery vacuum pump, a storage tank for storing the compressed recovered gas, and a rare gas for removing impurities in the recovered gas derived from the storage tank. A purifier that performs purification, characterized in that it is provided with a rare gas supply line that supplies the rare gas after purification to the rare gas using equipment, especially between the recovery vacuum pump and a compressor, Vacuum port for collection Provided with a detoxification device for detoxifying a target component contained in the recovered gas from which the recovery gas has been derived, and an impurity concentration detection means for measuring an impurity concentration in the recovered gas at a subsequent stage of the detoxification device. In addition, an exhaust line for exhausting the recovered gas according to the measured impurity concentration is branched between the impurity concentration detecting means and the compressor via a line switching means, and further, pressure detection is performed on the storage tank. And a rare gas replenishing means for introducing a rare gas into the storage tank in accordance with the value detected by the pressure detecting means.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a system diagram showing an embodiment in which the rare gas recovery device of the present invention is applied to a sputtering device which is a rare gas use facility. In addition, each component in the sputtering apparatus is denoted by the same reference numeral as the corresponding component of the sputtering apparatus shown in FIG. 4, and a detailed description thereof will be omitted.

The rare gas recovery device 31 forms a closed loop that recovers and purifies the rare gas discharged from the sputtering device 21 formed in the same manner as described above, and supplies the purified rare gas to the sputtering device 21 again. And a first evacuation pump 11a for evacuating the process chamber 1
And a second evacuation pump 1 provided in series on the secondary side thereof
1b, the recovery line 3 branched from the decompression line 17
2 and a rare gas supply line 33 that supplies a rare gas purified by the purifier 9 to the gas supply device 10, and is connected to the sputtering device 21.

The recovery line 32 and the pressure reducing line 17 are provided with a pair of switching valves 34a and 34b, respectively, as line switching means for switching the gas flow path. The switching valves 34a and 34b are opened and closed by commands output from the controller 12 according to the impurity concentration detected by the purity monitor 35 provided in the outlet path of the process chamber 1. One is opened and the other is closed. It opens and closes in conjunction so that For example, when the impurity concentration detected by the purity monitor 35 exceeds 100 ppm, the switching valve 34a
Is closed and the switching valve 34b is opened, so that the exhaust gas is
When the impurity concentration is 100 ppm or less, the switching valve 3
By closing the switch 4b and opening the switching valve 34a, an operation is performed to introduce the exhaust gas into the recovery line 32 of the recovery system. However, even if the impurity concentration is high, when a component contained in the impurity that can be removed by a removal device (abatement device) provided in the recovery system is included, this component is excluded.

In the sputtering apparatus 21 shown in this embodiment, a turbo molecular pump is used for the first evacuation pump 11a, and a dry pump or a screw pump is used for the second evacuation pump 11b. The pressure of 17 is in a reduced pressure state of about 100 Pa. The pressure in the process chamber 1 is 1 Pa
Degree, the pressure in the loading chamber 3 is 10-8 Pa
Set to about.

The rare gas recovery unit 31 includes a pressure reducing line 17
A vacuum pump 36 for collecting exhaust gas in a decompressed state, a removing device 37 for removing metal particles contained in the exhaust gas, a compressor 38 for increasing the exhaust gas to a predetermined pressure, A storage tank 39 for storing exhaust gas at a pressure, a purifier 9 and a rare gas container 16 for replenishing the rare gas are provided. When the equipment using the rare gas is equipment that uses harmful components such as a reactive gas, for example, a plasma CVD device or a reactive ion etching device, it is necessary to perform harm removal processing of harmful components contained in exhaust gas. Therefore, in addition to the removing device 37, a removing device using a removing agent (reactant, adsorbent, etc.) is installed.
This abatement device may be formed separately from the removal device 37, or may be formed integrally with the removal device 37.

Hereinafter, the method of the present invention will be described based on a procedure for recovering a rare gas. First, the wafer 2 before processing in the loading chamber 3 becomes substantially equal in pressure between the loading chamber 3 and the process chamber 1 so that the two chambers 1,
When the gate valve 7 separating 3 opens, it is set on the wafer susceptor 8 in the process chamber 1 through the gate valve 7. At this time, in order to prevent the back diffusion of impurities from the vacuum evacuation system, a purge gas is supplied from the purge gas supply unit 4 into the process chamber 1, and the pressure is maintained at a reduced level while the purge gas is supplied. Nitrogen is usually used as the purge gas, but the type of the purge gas may be selected according to the process, and is not limited to nitrogen.

After closing the gate valve 7 separating the chambers 1 and 3 from the gas molecules in the process chamber 1, a first vacuum pump (turbo molecular pump) connected to the process chamber 1 via a valve 18. The air is evacuated by a second evacuation pump (back pump) 11b connected thereto. Next, a rare gas from which impurities have been removed through the purifier 9 is introduced into the process chamber 1 at a flow rate of 500 cc / min through the gas supply device 10,
After setting the inside of the chamber to a rare gas atmosphere, high frequency is applied from the high frequency power supply 14 to generate plasma by high frequency discharge. The pressure at the time of occurrence of plasma is usually 1 Pa. The solid plasma deposition material is sputtered by the generated plasma and the wafer 2
A thin film is deposited thereon. The wafer 2 on which a predetermined thin film is formed is transferred from the process chamber 1 to the next process via the loading chamber 3 for the next processing. At this time, the rare gas used for depositing the thin film is pushed out of the process chamber 1 by the purge gas. In the above-described steps, loading and unloading of the wafer 2 is performed about 20 times per hour.

On the other hand, the exhaust gas from the process chamber 1 is evacuated through a valve 18 for isolating the process chamber 1 from the first evacuation pump 11a, and is exhausted by a purity monitor 35 installed upstream of the valve 18. The impurity concentration in the exhaust gas is measured. At this time, the purity monitor 35
Measures the impurity component in the rare gas, so that the in-situ measurement (in-situ measurement) can be performed to improve the recovery efficiency of the rare gas.
Measurement) is desirable. In addition, since the measurement is performed under reduced pressure, it is preferable to use a mass spectrometer as the purity monitor 35. By adopting the mass spectrometer, in-situ measurement becomes possible and rare gas can be removed. The measurement can be performed at a lower cost because unnecessary release to the outside of the system is not required, and installation is only required by providing a port in the exhaust pipe.

Although the purity monitor 35 is installed upstream of the valve 18 in this embodiment, it may be installed on the primary side of the switching valves 34a and 34b. At this time, the purity monitor 35
Any device can be used as long as it can perform in-situ measurement and can perform measurement under reduced pressure.
A spectroscopic analyzer using a T-IR or a laser as a light source can be suitably used.

The purity monitor 35 measures the concentrations of impurities such as oxygen, nitrogen, moisture, carbon monoxide, carbon dioxide, carbon fluoride, hydrogen, and various film forming gases in the exhaust gas. It is transmitted to the device 12. When the impurity concentration (the concentration of the impurity that cannot be removed by the removing device 37) becomes, for example, 100 ppm or less,
Preferably, the control device 1
The switching valve 34b provided upstream of the second evacuation pump 11b is closed by a signal from the second and the switching valve 34a provided in the recovery line 32 is opened, so that the flow of the exhaust gas is reduced from the pressure reducing line 17 in the reduced pressure state to the recovery line. 32, and the exhaust gas mainly composed of the rare gas is supplied to the rare gas recovery device 31.
Will be introduced. The flow path of the exhaust gas can be switched also on the primary side of the first evacuation pump 11a, but in this case, a pump having the same suction power as the turbo molecular pump is used as the recovery vacuum pump 36. There is a need.

The exhaust gas introduced into the rare gas recovery device 31 is sucked by the recovery vacuum pump 36 and sent to the removal device 37. The removal device 37 in the present embodiment is mainly for removing metal particles, and is mainly configured with a metal filter or the like. However, as described above, removal of harmful components contained in exhaust gas is performed. When performing the treatment, to remove the reactive gas molecules by oxidation reaction,
It mainly comprises an adsorbent for adsorption removal. In addition,
The reactants include copper oxide, iron oxide, nickel oxide,
Platinum and mixtures thereof can be used, and activated carbon, alumina, synthetic zeolite and the like can be used as the adsorbent, but are not limited thereto. When the reactive gas molecules are high-boiling compounds (boiling point is −50 ° C. or higher), the reactive gas molecules may be removed by liquefying or solidifying an appropriate cooling cylinder.

The exhaust gas that has passed through the removing device 37 is introduced into a compressor 38 and is subjected to a predetermined pressure, for example, 8 to 15 kg / cm.
It is pressurized to ² G. The compressor 38 is usually of a reciprocating type, but is not limited to this. The compressed exhaust gas is temporarily stored in a storage tank (buffer tank) 39 via a valve 38a on the secondary side of the compressor that operates simultaneously with the switching valve 34a and a check valve (not shown).

A pressure sensor 40 is provided in the buffer tank 39. When the pressure of the rare gas in the buffer tank 39 is equal to or lower than a predetermined pressure, for example, less than 2 atm, the pressure is controlled from the rare gas container 16 via the pressure control unit 41. Noble gas at an appropriate pressure is successively introduced. The capacity of the buffer tank 39 depends on the process chamber 1 and the volume from the process chamber 1 to the second evacuation pump 11b.
It is sufficient that the volume is equal to or larger than the volume between the process chamber 1 and the second vacuum pump 11b.

The rare gas stored in the buffer tank 39 is introduced into the purifier 9 via a valve 42, and the impurities in the rare gas, for example, water, nitrogen, oxygen, carbon monoxide, carbon dioxide, Hydrogen and various hydrocarbons are removed. As the purifier 9, various methods, for example, an adsorption method or a membrane separation method can be used, and a getter-type purifier using a metal or alloy such as titanium, vanadium, zirconium, iron, or nickel is preferable. is there. Here, since the impurity concentration in the rare gas is measured by the purity monitor 35 at the time of recovery, a rare gas having a known impurity concentration is introduced into the purifier 9. Usually, the performance (impurity removal efficiency) of the getter type purifier depends on the inlet impurity concentration and the superficial velocity, so that the impurity concentration is 100%.
If it is not less than ppm, it is necessary to reduce the superficial velocity, that is, to make the getter cylinder thick, and the purifier 9 becomes large. Therefore, if the impurity concentration is 100 ppm, preferably 10 ppm or less, the inner diameter of the getter cylinder may be about 30 mm when the standard processing flow rate is 1 liter per minute,
Miniaturization is possible. Further, it is also possible to appropriately perform an optimal design according to the required flow rate. Further, by providing the integrating flow meter in the purifier 9, the life of the getter can be calculated and the replacement time of the getter can be predicted.

The rare gas from which impurities have been removed by the purification device 9 is introduced into the process chamber 1 from the rare gas supply line 33 via the gas supply device 10, and is reused. As described above, the rare gas is used in the preliminary evacuation step immediately after the wafer 2 is introduced into the process chamber 1 and during the deposition of a thin film by plasma generation. For example, in the case of a 200 mm wafer, the volume is about 0.2 liter, and is collected according to the impurity concentration. On the other hand, the rare gas used at the time of depositing the thin film has a sufficiently low impurity concentration, so that all of the rare gas can be recovered and recycled.

As described above, according to the present invention, most of the rare gas used in the sputtering apparatus 21 can be recovered and circulated, so that the required amount of the rare gas can be used with the required purity and at low cost. it can.

That is, by switching the exhaust gas line between the recovery system and the exhaust system in accordance with the impurity concentration in the exhaust gas, the purifier 9 can be downsized and its life can be extended. Especially,
Switching by the pressure reducing line 17 in a reduced pressure state prevents the rare gas from staying in the pump section or the like, so that the rare gas discharged from the process chamber 1 can be efficiently collected. Further, as described above, since the impurity concentration becomes low during the deposition of the thin film, the rare gas can be efficiently recovered and reused by switching the exhaust gas line according to the operation state of the sputtering apparatus 21. Further, by replenishing the rare gas from the rare gas container 16 in accordance with the pressure in the buffer tank 39 at the time of the recovery operation, the required amount of the rare gas can be reliably replenished,
A single purifier 9 can purify a rare gas.

The compressor 38 is normally operated at a commercial frequency. However, since the pressure on the primary side of the compressor fluctuates in accordance with switching to the recovery system, a stable operation is performed. Requires that the primary and secondary sides of the compressor be bypassed and that a pressure regulator be provided in the system. However, in this method, the rare gas compressed by the compressor 38 is compressed again, so that the operating cost for compression may increase. In order to reduce the compressor operating cost, it is preferable to provide the compressor 38 with an inverter control mechanism. In this case, the compressor 38 can be operated in an optimal state based on a signal from a pressure sensor provided on the primary side of the compressor 38. That is, when the pressure on the primary side of the compressor is lower than the reference pressure, that is, when the amount of exhaust gas introduced into the recovery system is small, the frequency is controlled to be small, and when the pressure on the primary side of the compressor is higher than the reference pressure. Can control the pressure on the primary side of the compressor constantly while reducing the power consumption in the compressor 38 by performing control to increase the frequency. Becomes possible.

FIG. 2 shows an example in which a plurality of rare gas use equipment, for example, three sputtering devices 21 are connected to the rare gas recovery device 31. That is, the three recovery lines 32 branched from the decompression lines 17 of the respective sputtering devices 21 are connected to one main recovery line 51 downstream of the switching valve 34a, and the main recovery line 51 is connected to the recovery vacuum pump 36. And the rare gas supply line 33 is
It is connected to each sputtering device 21 via a branch line 52.

The structure, function and operation of the rare gas recovery device 31 are the same as described above, but by adjusting the operation cycle of each sputtering device 21, the rare gas recovery device 31 can be operated in a stable state. That is, assuming that a time required for a series of processes of wafer loading, film formation, and wafer unloading in each sputtering apparatus 21 is t,
By shifting the process start time of each plasma processing apparatus by t / 3, the amount of exhaust gas recovered through the main recovery line 51 can be averaged, and stable operation of the compressor 38 can be performed, and purification can be performed. The amount of the rare gas supplied from the vessel 9 via the rare gas supply line 33 can also be averaged. However,
The shift period (t / 3) can be appropriately set according to the equipment for using the rare gas and the process time, and an arbitrary shift period can be selected.

FIG. 3 is a diagram showing a plasma CVD apparatus or a reactive ion etching apparatus suitable for a rare gas using facility in which a film forming gas such as a reactive gas or an etching gas is mixed with a rare gas. FIG. 2 is a system diagram showing one embodiment of a rare gas recovery device. The main components of the rare gas recovery device and the rare gas use facility shown in this embodiment are the same as those of the rare gas recovery device 31 shown in FIG. 1 and the rare gas use facility (sputtering device 21). Therefore, the same components are denoted by the same reference numerals, and detailed description is omitted.

First, in the rare gas-using facility, a gas supply line 60 for film formation is provided downstream of the gas supply device 10, and a rare gas supplied from the gas supply device 10 and a gas supply gas for film formation are provided. A mixer 63 mixes a reactive gas supplied from a source 61 via a flow controller 62 and a film forming gas such as an etching gas, for example, a reactive gas such as monosilane, ammonia, and phosphine, and various doping gases. The gas is mixed and supplied to the process chamber 1 by the mixer 63.

On the rare gas recovery device side, in addition to the first line switching means 71 comprising the same switching valves 34a and 34b, a pair of switching valves 7 is provided upstream of the compressor 38.
A second line switching means 72 comprising 2a and 72b is provided, and an abatement device 73 is provided between the upstream side of the second line switching means 72 and the recovery vacuum pump 36.
And a purity monitor 74. The second line switching means 72 is formed such that the controller 75 opens and closes the switching valves 72a and 72b in accordance with the purity of the rare gas detected by the purity monitor 74, that is, the impurity concentration. When the concentration is sufficiently low, the switching valve 72a is opened and the switching valve 72b is closed, and when the impurity concentration is high, the switching valve 72b is opened and the switching valve 72a is closed.

In the apparatus having such a configuration, the wafer 2
In a process in which the rare gas and the film-forming gas are not introduced into the process chamber 1 as in the case of the replacement, the recovery-side switching valve 34a of the first line switching means 71 is in the closed state.
The switching valve 34b on the exhaust side is in an open state, and the purge gas, for example, nitrogen gas, which is supplied into the process chamber 1, is sucked by the turbo molecular pump 11a and led to the pressure reducing line 17, is supplied to the switching valve 34b, Pump 11b
Through the exhaust path 15 to the outside of the system.

When the introduction of the rare gas and the film-forming gas into the process chamber 1 starts, both the switching valves 34a and 34b in the first line switching means 71 are switched and opened, and the exhaust gas flowing through the pressure reducing line 17 is The liquid is sucked into the recovery vacuum pump 36 via the switching valve 34a. The exhaust gas led out from the recovery vacuum pump 36 is subjected to removal or detoxification processing of the components to be detoxified such as the metal particles and the reactive gas by the detoxification device 73, and then the purity of the rare gas (impurity concentration) by the purity monitor 74. ) Is measured. In this embodiment, since the installation position of the purity monitor 74 is a line in the atmospheric pressure state on the secondary side of the recovery vacuum pump, a gas chromatograph or the like is used as the purity monitor 74 in addition to the above-described various devices. Is also possible.

The impurity concentration measured by the purity monitor 74 is sent to the controller 75 and, as described above, the switching valves 72a, 72a of the second line switching means 72 according to the impurity concentration.
2b is switched and opened and closed. Exhaust gas with low impurity concentration
After passing through the switching valve 72a and being compressed to a predetermined pressure by the compressor 38, it is once stored in the buffer tank 39 in the same manner as described above, purified by the purifier 9, and supplied to the rare gas supply line 33.
Through the gas supply device 10 and the mixer 63 to the process chamber 1 again.

The exhaust gas having a high impurity concentration is supplied to the switching valve 72b.
Is opened and the switching valve 72a is closed, and is returned to the primary side of the back pump 11b via the exhaust line 76. Note that, in the present embodiment, a case where a film-forming gas that cannot be removed by the removal device 73 remains as an impurity contained in the gas discharged from the back pump 11b to the outside of the system via the exhaust line 76. Also, in consideration of the fact that the film forming gas remaining in the system flows into the exhaust system when the switching valve 34b is open, a preliminary abatement device 77 is also provided in the exhaust path 15, and the abatement process is also performed here. I'm trying to do it.

[0044]

Example 1 A xenon gas recovery operation was performed using a rare gas use facility and a rare gas recovery apparatus having the configuration shown in FIG. 1, and the recovery rate was measured. The xenon gas recovery rate depends on the pressure control unit 4
1 was calculated from the newly introduced amount measured by a flow meter provided downstream of the apparatus 1 and the flow rate used in the gas supply device 10. The main components of the rare gas recovery device are as follows.

Purifier 9: Ti alloy getter type Allowable pressure 10 kg / cm ² , use flow rate 1 liter per minute Buffer tank 39: SUS316L Internal volume 15 liter, Allowable pressure 10 kg / cm ² Pressure control unit 41: Piezo control pressure Control range 1.5 to 9.5 kg / cm ² Compressor 38: Reciprocating type Maximum pressurizing pressure 8 kg / cm ² , withstand pressure 15 kg / cm ²

Prior to the recovery operation, the rare gas recovery device was started up in the following procedure. First, the inside of the pressure control unit 41, the buffer tank 39, the compressor 38, and the purifier 9 is evacuated by a vacuum pump of a helium leak detector 81 connected to the downstream side of the buffer tank 39 as shown in FIG. A leak test was performed. Next, xenon gas was introduced from the rare gas container 16 via the pressure control unit 41 while the inside of each component was kept in a vacuum state. The introduction pressure was measured by a pressure sensor, and the pressure was increased to 3 kg / cm ² . Then, the purifier 9 and the compressor 38 were started, and the inside of the process chamber 1 was evacuated to 10 ⁻⁷ Pa. Using the rare gas recovery device thus started up, an operation of recovering the rare gas discharged from the magnetron sputtering device, which is a rare gas use facility, was performed.

In the magnetron sputtering apparatus, aluminum was used as a solid material for film formation. Also,
The gate valve separating the process chamber and the loading chamber was opened and closed only when loading and unloading the wafer, and the loading and unloading time of the wafer was set to 30 seconds. Before loading and unloading of the wafer, nitrogen gas was introduced as a purge gas into the loading chamber and the process chamber so that the pressure became 1 Pa. After placing the wafer in the process chamber, xenon gas was introduced at 1500 cc / min for 10 seconds to perform preliminary evacuation. Thereafter, plasma was generated at a pressure of 1 Pa while flowing xenon at a flow rate of 1500 cc / min, and film formation was performed for 1 minute. This process was repeated to process 6-inch wafers at a rate of 36 wafers / hour. In this experiment, since the gas was evacuated while constantly passing the gas into the process chamber, the back diffusion from the evacuation system could be prevented, and the specific resistance of aluminum between the processed wafers was:
It became almost constant.

It was confirmed by a purity monitor that the xenon gas was replaced with the nitrogen gas in a few seconds when the wafer was loaded into and unloaded from the process chamber. Similarly, in the preliminary evacuation step, impurities mainly composed of nitrogen gas were replaced by xenon gas. During the preliminary exhaust process, the impurity concentration becomes 1
Although it became 0 ppm or less, xenon gas was not collected in the preliminary exhaust process, but was collected only during film formation.
The amount of new xenon gas introduced is 9000c per hour
c. The total amount of gas introduced into the process chamber is 63
Since it is 000 cc, the recovery rate is about 86%.

Example 2 A plasma CVD apparatus for forming a polycrystalline silicon film was used as an equipment using a rare gas. The configuration of the plasma CVD apparatus is the same as that shown in FIG. 1 except that a gas supply line 60 for film formation as shown in FIG.
And monosilane was used as a film forming gas. The substrate is a 300 mm square glass substrate,
The substrate temperature was 300 ° C. The gate valve that separates the process chamber from the loading chamber was opened and closed only when loading and unloading the wafer, and the loading and unloading time of the wafer was 30 seconds. Before loading and unloading wafers, nitrogen gas is introduced into the loading chamber and the process chamber,
00Pa. After placing the wafer in the process chamber, xenon gas and monosilane gas were
Preliminary evacuation was performed at a rate of 0: 1 at a rate of 1000 cc / min for 10 seconds. Thereafter, the xenon gas and the monosilane gas were mixed at a pressure of 100 Pa and a total flow rate of 3 at a ratio of 100: 1.
The film formation was performed for 110 seconds while flowing at a flow rate of 000 cc / min. This process was repeated and processed at a rate of 24 sheets / hour. In this experiment, film formation was performed while changing the total flow rate during film formation from 300 cc / min to 3000 cc / min, and the surface flatness, uniformity, and crystallite size of polycrystalline silicon were measured. As a result, 3000cc /
Min was best performed.

The purity monitor confirmed that the xenon gas was replaced with nitrogen gas in a few seconds as the wafer was loaded into and unloaded from the process chamber. In the preliminary evacuation step, impurities mainly composed of nitrogen gas were replaced with xenon gas and monosilane gas. And was replaced by When the concentration of impurities other than the monosilane gas became 10 ppm or less during the preliminary evacuation step, the collection of xenon gas was started. No monosilane gas component was observed in the exhaust gas during the film formation.
This is because the monosilane gas was completely decomposed by the high-density plasma. The amount of new xenon gas introduced is
It became 3960 cc per hour. Since the total amount of gas introduced into the process chamber is about 134650 cc, the recovery rate is about 97%.

Example 3 As a rare gas using facility, a plasma CVD apparatus for forming a film of doped polycrystalline silicon was used. As in Example 2, a film forming gas supply line was attached to the apparatus having the configuration shown in FIG. 1, and monosilane was used as the film forming gas, and phosphine was used as the doping gas. The substrate is 3
The glass substrate was a 00 mm square, and the substrate temperature was 300 ° C. The gate valve that separates the process chamber from the loading chamber was opened and closed only when loading and unloading the wafer, and the loading and unloading time of the wafer was 30 seconds. Before carrying out the wafer, the nitrogen gas was introduced into the loading chamber and the process chamber so that the pressure became 100 Pa. After the wafer is set in the process chamber, xenon gas, monosilane gas, and phosphine gas are mixed for 1000 times.
00: 1000: 1 at 1000 cc / min.
Preliminary evacuation was performed by introducing for 2 seconds. After that, pressure 100P
In a, film formation was performed for 160 seconds while flowing xenon gas and monosilane gas at a ratio of 100: 1 at a total flow rate of 3000 cc / min. By repeating this step, 1
Processing was performed at a speed of 8 sheets / hour.

With the transfer of the wafer into and out of the process chamber, the xenon gas was replaced with nitrogen gas within a few seconds, and in the preliminary evacuation step, impurities mainly composed of nitrogen gas were replaced with xenon gas and monosilane gas. Although the impurity concentration other than the monosilane gas and the phosphine gas became 10 ppm or less during the preliminary evacuation step, xenon gas was not collected in the preliminary evacuation step, but was collected only during film formation. No monosilane gas or phosphine gas component was observed in the exhaust gas during film formation. This is because the monosilane gas and the phosphine gas were completely decomposed by the high-density plasma. The amount of new xenon gas introduced was 2970 cc per hour. The total amount of gas introduced into the process chamber is about 145540 cc
Therefore, the recovery rate is about 98%.

Example 4 In the apparatus configuration shown in FIG. 3, a plasma CVD apparatus for forming a silicon nitride film was used for the equipment using a rare gas, and monosilane and ammonia were used for the film forming gas. Also,
The substrate is a 300 mm square glass substrate, and the substrate temperature is 3
The temperature was set to 00 ° C. The gate valve that separates the process chamber from the loading chamber was opened and closed only when loading and unloading the wafer, and the loading and unloading time of the wafer was 30 seconds. Before loading and unloading the wafer, nitrogen gas was introduced into the loading chamber and the process chamber so that the pressure became 100 Pa. After placing the wafer in the process chamber,
Xenon gas, monosilane gas and ammonia gas
Preliminary evacuation was carried out at a rate of 00: 1: 5 at a rate of 1000 cc / min for 10 seconds. Then, at a pressure of 100 Pa,
Xenon gas, monosilane gas and ammonia gas
Film formation was performed for 160 seconds while flowing at a flow rate of 00: 1: 5 at a total flow rate of 3000 cc / min. This process was repeated and processed at a speed of 18 sheets / hour.

As the wafer is loaded into and unloaded from the process chamber, the process gas containing xenon gas as a main component is replaced with nitrogen gas in a few seconds. Replaced by ammonia gas. At the time of the preliminary evacuation step, xenon gas was not collected, and xenon of the exhaust gas was collected only at the time of the film formation step. In a preliminary experiment conducted in advance, no monosilane gas component could be detected in the exhaust gas during film formation, but about 10% of the ammonia gas component was detected.
About 00 ppm was detected. The nitrogen gas component is 10
It was 0 ppm or less. Ammonia gas is removed by the abatement device installed on the secondary side of the vacuum pump for recovery.
Even if the ammonia content is large, xenon gas can be recovered from the exhaust gas during the film formation step. Since the amount of new xenon gas introduced is 2830 cc per hour and the total amount of gas introduced into the process chamber is about 135850 cc, the recovery rate is about 98%.

Example 5 As a rare gas, an argon gas was used instead of xenon gas, and a reactive ion etching apparatus for etching boron phosphorus glass (BPSG) was used as a rare gas using facility. C ₄ F for etching gas
₈ and carbon monoxide and oxygen were used. Also, the substrate is
This is an 8-inch Si wafer on which BPSG is deposited at a thickness of 1.5 μm, and a mask material called a resist is placed on the substrate at a thickness of 0.1 mm.
7 μm was applied, and a hole pattern having a diameter of 0.18 μm was formed on the mask material through exposure and development processes. The device configuration was the same as in Example 2.

The gate valve that separates the process chamber from the loading chamber is opened and closed only when loading and unloading the wafer, and the loading and unloading time of the wafer is set to 30 seconds. Before loading and unloading of the wafer, nitrogen gas was introduced into the loading chamber and the process chamber so that the pressure was 5 Pa. After placing the wafer in the process chamber, gas _{ratio, C 4 F 8: 5%} , CO: 15%, oxygen: 2% and argon: 78% of the gas, at a total flow rate of 500 cc / min 10
Preliminary evacuation was performed by introducing for 2 seconds. After that, pressure 5Pa
And the total flow rate of the process gas of the gas ratio is 1000 cc /
The etching was performed for 1 minute while flowing at a flow rate of 1 minute. This process was repeated and processed at a rate of 36 sheets / hour.

The process gas was replaced with nitrogen gas in a few seconds as the wafer was loaded into and unloaded from the process chamber. In the preliminary exhaust process, the nitrogen gas was replaced by the process gas. In this preliminary exhaust process, argon was recovered. Did not. In a preliminary experiment conducted in advance, a C—F compound, SiF ₄ , carbon dioxide, and argon were mainly observed as gas components during film formation, but oxygen was consumed for oxidation of CO and the resist, and almost all were measured. Was not done. Since reactive gas molecules other than oxygen and argon can be removed by the abatement apparatus, argon gas was recovered during film formation irrespective of their contents. The amount of new argon gas introduced is 2380 cc per hour, and the total amount of gas introduced into the process chamber is about 30420 cc.
%.

[0058]

As described above, according to the present invention,
The rare gas in the exhaust gas discharged from a rare gas using facility such as a plasma processing apparatus can be recovered with high efficiency, and a required amount of the rare gas can be circulated and used at a required purity at a low cost. In addition, by recovering under reduced pressure while measuring the impurity concentration in the rare gas to be recovered, the recovery efficiency is improved and an excessive load is not applied to the purifier for removing the impurities.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment in which a rare gas recovery device of the present invention is applied to a sputtering device.

FIG. 2 is a system diagram of a main part showing a connection example when applying the rare gas recovery device of the present invention to a plurality of rare gas use facilities.

FIG. 3 is a system diagram showing an embodiment in which the rare gas recovery device of the present invention is applied to a rare gas use facility that uses a film forming gas.

FIG. 4 is a system diagram illustrating an example of a plasma processing apparatus.

FIG. 5 is a system diagram showing an example of a conventional rare gas recovery device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Process chamber, 2 ... Wafer, 3 ... Loading chamber, 4 ... Purge gas supply part, 5 ... Gate valve, 6
a, 6b: vacuum pump, 7: gate valve, 8: wafer susceptor, 9: purifier, 10: gas supply device, 11a ...
1st evacuation pump, 11b ... second evacuation pump, 1
2 ... control device, 13 ... matching circuit, 14 ... high frequency power supply, 1
5 exhaust path, 16 rare gas container, 17 pressure reducing line,
21: sputtering device, 31: rare gas recovery device, 3
2: recovery line, 33: rare gas supply line, 34a, 3
4b: Switching valve, 35: Purity monitor, 36: Recovery vacuum pump, 37: Removal device, 38: Compressor, 39: Storage tank (buffer tank), 40: Pressure sensor, 41: Pressure control unit, 51: Main Collection line, 52 branch line, 60 gas supply line for film formation, 61 gas supply source for film formation, 62 flow rate regulator, 63 mixer, 71 line switching means, 72 second line Line switching means, 7
2a, 72b: switching valve, 73: abatement device, 74: purity monitor, 75: controller, 76: exhaust line, 77: preliminary abatement device

Claims (8)

[Claims] When recovering a rare gas in an exhaust gas discharged from a rare gas-using facility operating under reduced pressure, the operation of switching the introduction of the exhaust gas to a recovery system and the discharge of the exhaust gas to an exhaust system is performed by the exhaust gas A method for recovering a rare gas, which is performed according to the concentration of an impurity component contained therein. 2. When recovering a rare gas in an exhaust gas discharged from a rare gas using facility operated under reduced pressure, switching between introduction of the exhaust gas into the recovery system and discharge into the exhaust system in a reduced pressure state. A method for recovering a rare gas. 3. The rare gas according to claim 2, wherein the switching operation between the introduction of the exhaust gas into the recovery system and the discharge into the exhaust system is performed in accordance with the concentration of the impurity component contained in the exhaust gas. Gas recovery method. 4. The operation of switching a rare gas according to claim 2, wherein the switching operation between the introduction of the exhaust gas into the recovery system and the discharge into the exhaust system is performed in accordance with the operation state of the rare gas use facility. Collection method. 5. A rare gas using facility operated under reduced pressure, a first evacuation pump for sucking exhaust gas discharged from the rare gas using facility, and a decompression line on a secondary side of the first evacuation pump. A second evacuation pump provided in series via a pump, a recovery line branched from the decompression line via line switching means, a recovery vacuum pump provided on the recovery line, and the recovery vacuum pump. A compressor for increasing the pressure of the recovered gas, a storage tank for storing the compressed recovered gas, a purifier for purifying the rare gas by removing impurities in the recovered gas derived from the storage tank, A rare gas supply line for supplying a rare gas to the rare gas use facility. 6. A detoxification device for removing detoxification target components contained in a recovered gas derived from the recovery vacuum pump is provided between the recovery vacuum pump and the compressor. The rare gas recovery device according to claim 5. 7. An impurity concentration detecting means for measuring an impurity concentration in the recovered gas is provided at a subsequent stage of the abatement apparatus, and between the impurity concentration detecting means and the compressor,
7. The rare gas recovery apparatus according to claim 6, wherein an exhaust line for exhausting the recovered gas according to the measured impurity concentration is branched via line switching means. 8. The storage tank according to claim 5, further comprising a pressure detecting means, and a rare gas replenishing means for introducing a rare gas into the storage tank in accordance with a value detected by the pressure detecting means. An apparatus for recovering a rare gas as described above.